The biochemical properties of DNA helices are determined by their structural properties in solution. In particular, the conformation of the sugar-phosphate backbone of DNA is likely to be important in the recognition of specific sequences by proteins and enzymes, but experimental methods that are capable of providing high resolution structural information about DNA helices in solution have not been described. In this application isotopic labeling and NMR spectroscopic methods are described that will allow the conformation of the sugar-phosphate backbones in double helical oligonucleotides to be accurately specified; this methodology represents a significant advance over presently used NMR techniques. D-Ribose that is labeled in the 1-, 3-, and 5-carbons with C13 will be chemically prepared; established chemical procedures will be used to incorporate this material in specific deoxyribose units in double helical oligonucleotides. One- and two-dimensional NMR techniques that utilize the C13 labeled sites as specific filters for observation of only those H1 NMR resonances that are directly coupled to C13 or are one carbon removed from the C13 will permit the H1 NMR spectrum of the labeled deoxyribose residue to be specifically observed; the coupling constants present in the spectra will allow the sugar pucker and the geometries of the phosphodiesters linkages to be described. The C13 labeling will also allow assignment of the P13 NMR resonances of the phosphorus atoms that are associated with the labeled deoxyribose unit. Using these methods, the conformations of the sugar-phosphate backbones in B- and Z-DNA, in heteroduplexes containing base pair mismatches and structural lesions, and in complexes of duplexes with actinomycin D will be examined.